1. Field of the Invention
The present invention relates to a temperature sensor having a temperature sensor element surrounded by a metallic cover, and to a method for producing the temperature sensor.
2. Description of the Related Art
Patent Document 1 discloses a temperature sensor having a metallic cover, a cylindrical insulator surrounded by the metallic cover, a thermistor element disposed in the cylindrical insulator, and an inorganic adhesive agent filled in the cylindrical insulator. However, due to recent demand for a temperature sensor which can generate sensor signals highly responsive to ambient temperature changes, the temperature sensor disclosed in Patent Document 2 has been developed. This sensor, in which an insulator or an inorganic adhesive agent filled therein are omitted, has a metallic cover of smaller external diameter so that the distance between the metallic cover and a temperature sensor element is reduced. In Patent Document 2, the metallic cover has a stepped-shape front portion of smaller inner diameter than the external diameter of a front end of a sheath pin (MI or mineral insulated cable) 5. On the other hand, in Patent Document 2, the electrode wires are separated by means of an insulator that avoids electrode wire breakage due to vibration of a thermistor element (temperature sensor element).
[Patent Document 1] Japanese Patent Application Laid-Open (kokai) No. H11-218449 (FIG. 1 on page 4)
[Patent Document 2] Japanese Patent Application Laid-Open (kokai) No. 2002-267547 (FIGS. 2 and 3 on page 3)
3. Problems to be Solved by the Invention
However, because the temperature sensor of Patent Document 2 requires its insulator member to be inserted into a metallic cover, the external diameter of the insulator member 6 is restricted in size so as to be smaller than the internal diameter of a portion corresponding to the metallic cover (the front portion in Patent Document 2). As a result, a gap remains between the metallic cover and the insulator member. When the temperature sensor is subjected to vibration, the electrode wires are prone to break in a region between the temperature sensor and the insulator member due to independent vibration of the temperature sensor and the insulator member in the metallic cover.